Conventionally, noise countermeasures have been taken against random telegraph signal (RTS) noise occurring in transistors, in image sensors and the like. For example, a method is considered in which an input transistor in a differential stage is increased in size in an A/D converter. However, there is a risk of occurrence of another noise such as aggravated noise resulting from a kickback or simultaneous inversion of comparator output. Also, a method is considered which uses, for example, a built-in transistor. However, there is a need to modify a process, and is a risk of increasing cost.
Also, in a case of an image sensor, RTS noise is noticeable as a vertical streak in a picked-up image obtained with the image sensor, and therefore, a method is considered in which noise is injected on purpose to relatively reduce an effect of the RTS noise (for example, see Patent Document 1).